1. Field of Invention
This invention relates to foot pedal control mechanisms and apparatus, and more particularly, to a method for engaging and disengaging a power take-off unit associated with the transmission of a heavy duty motor vehicle.
It is well known to those skilled in the art to utilize a so-called power take-off unit in conjunction with a truck or tractor transmission to provide power to a take-off shaft independent of the drive shaft of the vehicle. The power take-off shaft is used to operate an accessory device such as a hydraulic pump or other equipment carried on the vehicle.
In the conventional practice, the power take-off shaft must be engaged and/or disengaged by manual operation of a control lever coupled to a mechanical linkage to actuate the power take-off shaft. An example of such a manually controlled power take-off control mechanism is disclosed by U.S. Pat. No. 2,175,188 to Fuller. This patent discloses a foot pedal operated linkage which directly controls cutting in of a power take-off shaft independently of the propulsion shaft of the vehicle.
A particular problem with such a power take-off control mechanism is that the same must be manually disengaged after operation of the power take-off is complete and normal operation of the vehicle's propulsion shaft is to be resumed.
Since the power take-off shaft is designed to operate at lower revolutions per minute (rpm) than the vehicle's propulsion shaft, the power take-off unit shaft and accessory pump can be severely damaged if the operator fails to disengage the same prior to operating the vehicle at normal driving speed.
Thus, the present invention provides a power take-off release mechanism that is interconnected with the vehicle clutch pedal to automatically disengage the power take-off shaft whenever the vehicle is to be operated at normal driving speeds.
2. Description of Related Prior Art
U.S. Pat. No. 2,175,188 to Warren Fuller discloses an invention for control accessibility providing greater access for cutting-in and out one or more power driven means as from a tractor power plant.
U.S. Pat. No. 2,309,454 to Clifford M. Heller discloses a control mechanism and actuating apparatus for controlling the braking mechanism of an automotive vehicle. This invention includes a lever and clutch arrangement being so arranged that the clutching means for retaining the lever mechanism in adjusted position may be rendered effective or ineffective at will.
U.S. Pat. No. 2,455,233 to Shirley C. Copeland discloses an automatic throttle control adapted for use on tractors which is adapted to be actuated by the depressing of the tractor clutch to reduce the supply of the fuel mixture to the carburetor to cause the tractor engine to slow down to an idling speed.
U.S. Pat. No. 2,555,417 to Cebal F. Martin discloses a hand controlled clutch and brake for tractors providing a remote control connection whereby the operator of the tractor can operate the clutch and brake while standing up on the drawbar of the tractor or when standing on the ground as when the connection is being affected with a tractor drawn implement.
U.S. Pat. No. 2,277,312 to Henry Fehr discloses a foot actuated linkage terminating in a clutch operated lever and having a support adjacent the draw bar of the tractor, the clutch operating lever being directly over the center of the drawbar.
Finally, U.S. Pat. No. 4,608,879 to Mikio Ishida, et al., discloses a change speed operating apparatus for a tractor which may carry out an accelerating operation without losing the functions of a speed setting mechanism and automatically reset the speed setting mechanism at the previously set traveling speed after the acceleration.